Electric discharge device



Aug. 8, 1950 V.'L. HOLDAWAY v ,5

ELECTRIC DISCHARGE DEVICE Filed Oct. 29, 1947 IINVENITOR -14 L,-HOLDAWAV ATTORNEY Patented Aug. 8, 1950 Ewcrcrc DISCHARGE DEVICE Vivian I 1...HirldawawMidlandPark, N. J.,; assignor to Bell '-.lpelephonc.v Laboratories, Incorporated, New York, 12., a corporation of New York lipplicationfictdbenw, 194w; Seriat N0..782",702-

' Ihis invention-relatesvto. electric discharge: devices-and more. particularly tmsuchdeyicesi or the com: cathode type: and especiallycsuitable for" use 'ihg: control refementsz for mmtr-party-sel'ectiwetelephone: systems.

Discharge devices: ot" the type to which this invention pertains comprise m genera/B a. main cathode, a main or work anode, an auxil-i'ary cathode, and an auxiliary or control anode all within aresselfhazvin g a filling of. a suitable gas. In theoperaticn of the device, a discharge is initiated: between the auxiliary cathod c: andzcontool, anode Them the; discharge is caused to transfer to. the gap between. the; auxiliary oathcde' andi theuuta-in anode. This; is; known as the anode Finallmthe discharge. iacaused to. transfer to. the: gap.- between the main; cathode thelmainanodei. Thisi's lm'own asthe cathodetransfor.

order to preventdi'alse operation, it; is: desirdolaime. (c1. sac-27:5)

able: that the breakdown voltage between the w anodea-nd'the other electrodes and between iarywcathode main: anode gap to the main: cathode-main anode gap be relatiwiy low. These two: desiderata; are in a sense. opposition in i so tar" as electrode construction and spacingare mvawec lit is: desirable also, in: lord-onto expedite manu flacture of devices of thee-type and general con" -s'truction above-noted and reduce the cost g thereof, that the two cathodes be processed simultaneously. The processing involves high frequency heating of these electrodes-and because of their difierent sizes;- the auxiliary cathode being much-smallerthan the main cathode, there is: danger or damage to the. maincathodeby overheatingor deieteriousefiects uponthe auxilmy cathode by underheating;

onecba cc or this invention is; to improve the ouster characteristics: of multigap gaseous dis-- charge devices. )I

More specific-any; one object of this: invention to realize: transter ofl the discharge. to: the main anode-main cathode path at a. relatively low potentialidifierence'between the main." and, atrxil iany cathodes, concomitantly with thesatiiain ment: of a high breakdownsvoltage betweerr each or the main: .anoderand; main; cathode and other electrodes.

simultaneous. high frequency processing. of. both the: mainland.- auxiliary cathodes. H

In accordance with one feature of this invention; in a. discharge device of the type. andconstnuction above-described, means are proyided for causing. the auxiliary cathode tomain. anode discharge to follow a path, portions. of which arevrelatinely closeto-the maincathode whereby transfer of the discharge to the main cathode.- mainanode-gap'occursfor a relatively low potential difierence between the main. and auxiliary cathodes. V y

More specifically; accordance one; teaturecl this mventioman insulatingbafileor harrier. is provided between the: auxiliary cathode andmain anode.- and is positioned so. that. the discharge between these: two: electrodes passes around a. side edge of. the barrier" toward the main cathode, v v

In accordance with another feature) or. this invention; the main andauxiliary cathodes are constructed and arranged so that both may be heated: simultaneously by high freduency induction to: the temperature requisite toeffiect proper processing thereof. without; deleterious heating of. the main; cathode.

The invention and the; above-noted and other matures thereof will be understood more clearly and fully from the; followingdetaileddescription with. reference; to the. accompanying drawing: in which:

Fig; 1 is; a. perspective viewof an electric discharge device; illustrative of one embodiment. of invention. a portion of: the. enclosing vessel being; broken away to show the internal structunesmore clearly;

Fig... 2. is aplani viewof the device; with. a portionofi' the vessel removed; and

3V is a circuit. diagram illustrating one manner in; which the. discharge:- device show in Fig-s. it and Emery be utilized.

.Referrihgr now to; the drawing, the discharge device illustrated in, Figs. 1 and. 2 comprise a vitreous: enclosing vesset la secured. to a; base H and havtng: therein a filling of a. gas such as; a 15.0 cent arg.o11,. 90 per centneonz. mixture,- at a pressure of 55 millimetersof mercury or a single gas suclras argon: at. a pressure or 15 millimeters of: mercury. The: vessel. has: exhaust; tubulature I54, shown in Fig; .2; which. is enclosed by a cap 12. on the base, and has" sealed in its base wall; a. plurality of parallel metallic. rods having terminal portions t3 through which. electrical connection. to the electrodes: of the device may Anotherchject or this. imzentim is; taenahle- 55 bea'estaiblished:

Two of the rods I'5 mount the main cathode which comprises a pair of arcuate, sheet metal, e. g. nickel, members It having metallic projections or flanges I? through which the rods l5 project, the two juxtaposed flanges being secured together, as by welding, and the cathode being affixed to the rods by metal strips [8 welded to the cathode members l6 and to the rods. The concave faces of the cathode members I6 have thereon a coating of electron emissive material; the convex faces and flanges may be calorized to prevent conduction therefrom.

Disposed opposite the concave cathode surface and uniformly spaced therefrom is a rod electrode 89. which is supported from the rod 20 and is utilized as an activating anode, in known manner, in the activation treatment of the electron emissive coating during the manufacture of the device. Also supported from the rod 2E3 is a disc 21 which carries a quantity of getter material 22 on the outwardly facing surface thereof.

Another of the rods 23 is opposite and relatively widely spaced from the emissive face of the main cathode and constitutes the main anode of the device. The lower portion of this rod is encompassed by an insulating, e. g. glass or ce ramic, sleeve 24 which is held in place by a retaining band or collar 25 afiixed, as by welding, to the rod 23.

Facing the main anode 23 is the auxiliary cathode which is in the form of a metal plate 25 the face of which toward the anode 23 is coated with electron emissive material. The auxiliary cathode is supported from the rod 21 by a U-shaped sheet metal projection, bracket or flange 28 which is fixed in place upon the rod by a U-shaped wire 29 welded to the bracket and the rod. The bracket 28 and rear face of the auxiliary cathode 26 are caloriz'ed to prevent conduction therefrom.

'Ihe auxiliary or control anode is constituted by the rod 30 and, as shown most clearly in Fig. 2,'ispositioned opposite the emissive face of the auxiliary cathode 26 and in juxtaposition to one of the side edges thereof.

An insulating, e. g. mica, sheet baffle or barrier 3| extends across the gap between the main anode 23 and the auxiliary cathode 26. One side of the barrier is in proximity to the side wall of the vessel It, as shown in Fig. 2, and the barrier extends a substantial distance 'above and below the auxiliary cathode, as shown in Fi 1.

affixed to the anode 23 and rod 34 respectively.

The operating characteristics of the device are dependent largely upon the electrode spacings. The spacing between the main anode 23 "and main cathode [6 is made such as to provide the desired breakdown voltage for the gap therebetween. Similarly, the control elements, that is the auxiliary cathode 26 and control anode 30, are spaced relative to the main cathode IE to provide the desired breakdown voltage requirements therebetween. Also, the main anode to auxiliary cathode spacing is fixed to meet the breakdown voltage requirements, this spacing being less than it would be if the barrier or bafile 3| were absent. The control anode is placed in immediate proximity to the auxiliary cathode, e. g. spaced of the order of 0.010 inch therefrom, to produce a low breakdown voltage in the control gap. The position of the control anode relative to the control cathode is such that it does not mask the emissive face of the control cathode and also causes the conducting area and associated ionized gas to be exposed to the field of the main anode and main cathode, thereby effecting low transfer conditions for both the anode transfer and the: cathode transfer. "In general, in-the operationof the device, the main or work anode is biased positively with respect to the other electrodes. Upon the application of a prescribed potential between the control anode and auxiliary cathode, the gap between these elements breaks down and the discharge is transferred to the gap between the auxiliary cathode and the main anode. This discharge, as has been pointed out heretofore, is directed along a path, around the edge of the barrier or baffle 35, toward the main cathode [6. It has been found that as a result of this effect, transfer of the discharge from the auxiliary cathode-main anode gap to the main cathodemain anode gap can occur at a much lower difference inpotential between the twocathodes than would be necessary if the baffle or barrier were not present. Ina typical case a reduction of the order of 30 volts, i. e. from about 60 volts to 30 volts, in this potential difference has been realized.

One application of the discharge device, specifically as a ringing control in 4-party line telephonesystems, is illustrated in Fig. 3. The main cathode i6 is grounded, as shown, and the auxiliary cathode 26 is connected to the telephone line conductor 35 through a resistor 33. The main anode 23 is connected, in series with the ringer 31, to the other line conductor 38 and the control anode 30 is connected to this conductor through a resistor 39. The line "conductors lead to terminals at a central-office, indicated to the right of the line XX in Fig. 3, one of the terminals being grounded directly and the other terminal leading to a biasing battery 6i] and ringing current source 4!. For the positive party on ring, the conductor 35 is connected to the grounded terminal and the conductor 38 is connected to the terminal leading to the source M. The voltage due to the source 50 is insufficient to effect breakdown of the control anode-auxiliary cathode gap. However, when the voltage due to source ii, which may be of sine wave form, together with that due to the source 40 reaches a prescribed value, conduction in the control anode-auxiliary cathode gap is initiated'and as the voltage increases, in the positive half of the cycle of source 41, the current in this gap increases. The potential of the main anode 23, when no ringer current is flowing, follows that of the line 38 and the potential difference between the control cathode and :main anode is equal to that of line 33 minus the drop in the auxiliary cathode resistor 36. As the control gap current increases, a condition is reached, early in the cycle, when transfer of the discharge to the auxiliary cathode-main anode gap occurs.

The impedance of the ringer 3'! is much smaller than that of the control anode resistor 39. Hence, when the aforenoted transfer occurs, the current in the auxiliary cathode-main anode gap is greater than that which flowed in the control gap and the drop in the cathode resistor 36 increases rapidly as the line voltage" increases. Consequently, the potential of the auxiliary cathode relative to the main cathode likewise increases and when this potential reaches a certain value, transfer of the discharge to the main cathodemain anode gap occurs. Ringing current continues to flow as long as the line voltage remains above the sustaining voltage of the main cathode-main anode gap.

In the manufacture of the device, it is necessary to outgas the several electrodes. As to the two cathodes, this may be accomplished most conveniently by radio frequency induction hea ing through the agency of a coil positioned about the vessel in for producing a radio frequency field parallel to the axis of the vessel. It will be appreciated that both cathodes should be heated to the same temperature to effect the desired outgassing thereof. Most of the heating current induced in the main cathode l6 results from interception of the radio frequency field by the flanges l1; similarly much of the heating current induced in the auxiliary cathode 26 results from interception of the radio frequency field by the bracket 28. The combination of the bracket support 28 and the flanged cathode members enables correlation of the effective heating areas of the two cathodes so that despite the large difference in the sizes of the two cathodes the two can be heated simultaneously to the same temperature and thus concurrently denuded of occluded gases.

Although a specific embodiment of the invention has been shown and described, it will be understood that it is but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An electric discharge device comprising an enclosing vessel having an ionizable atmosphere therein and housing a main anode, a main cathode opposite said anode, an auxiliary cathode opposite said anode, a control electrode adjacent said auxiliary cathode, and baflle means mounted between said anode and said auxiliary cathode for directing the discharge between said auxiliary cathode and anode into a path passing into proximity to the gap between said main cathode and said anode.

2. An electric discharge device comprising an enclosing vessel having an ionizable atmosphere therein and housing a main anode, a sheet auxiliary cathode opposite said anode, a main cathode opposite one side edge of said auxiliary cathode, a control electrode in proximity to the face of said auxiliary cathode toward said anode, and an insulating barrier means mounted between said anode and said auxiliary cathode for directing the discharge therebetween into a path toward said main cathode.

3. An electric discharge device comprising an enclosing vessel having an ionizable atmosphere Q main cathode, the device comprising also a control electrode in juxtaposition to the opposite side edge of said auxiliary cathode.

5. An electric discharge device comprising an enclosing vessel having an ionizable atmosphere therein and housing a main cathode having an arcuate concave emissive face, an insulating sheet spaced from and having one side edge toward said face, a rod anode opposite one face of said sheet, and an auxiliary cathode opposite the other face of said sheet and having an emissive surface facing said other face.

6. An electric discharge device in accordance with claim 5 wherein said auxiliary cathode is of plate form and has one side edge toward said concave face, the device comprising also a rod control electrode in juxtaposition to the other side edge of said auxiliary cathode.

7. An electric discharge device comprising an enclosing vessel, a pair of electrodes within said vessel, said electrodes being of unequal sizes, flange means extending from the larger of said electrodes substantially normal to the major surfaces thereof, other flange means extending from the smaller of said electrodes substantially normal to the major surfaces thereof, said flange means being of unequal sizes effecting inductive heating of said electrodes by a high frequency field substantially parallel to said major surfaces simultaneously to substantially the same temperatures, and means cooperating with said flange means to support said electrodes in said vessel.

8. An electric discharge device comprising an enclosing vessel, a pair of sheet metal cathodes within said vessel and extendin parallel to an axis thereof, one of said cathodes being substantially larger than the other, and means for effecting simultaneous heating to substantially the same temperature of both said cathodes by a high frequency field parallel to said axis, said means comprising metallic projections on both said cathodes extending in directions at angles to said axis, said projections being of different sizes, whereby the effective heating areas of the two electrodes are correlated.

9. An electric discharge device comprising an enclosing vessel, a pair of sheet metal cathodes within said vessel and extending parallel to an axis thereof, one of said cathodes being substantially larger than the other, an anode opposite one face of each of said cathodes, and metallic projections extending substantially normal from the opposite face of each of said cathodes, said projections being of different sizes, whereby the effective heating areas of the two electrodes are correlated to effect simultaneous heating of the two cathodes to substantially the same temperature by a high frequency field parallel to said axis.

VIVIAN L. HOLDAWAY.

REFERENCES CITED UNITED STATES PATENTS Name Date Von Wedel Oct. 18, 1932 Number 

